This invention relates generally to vehicle fuel systems and more particularly to a vapor vent and rollover valve for a vehicle fuel tank and a fuel pump module incorporating such a vapor vent and rollover valve.
Environmental concerns and governmental regulations require reduced emissions of volatile hydrocarbon fuel vapors into the atmosphere. One source of hydrocarbon fuel vapors is fuel tanks of vehicles using gasoline or other hydrocarbon fuels with high volatility. Fuel vapor can escape to the atmosphere during the filling of the tanks and usually, even after the tanks are filled. The use of an onboard vapor recovery system to remove excess fuel vapor from the fuel tank is one solution to the problem. Typically, a canister with activated charcoal therein receives fuel vapors through a valve assembly mounted in the top of the fuel tank and communicates with the intake manifold of the vehicle engine for withdrawing fuel vapor from the canister during operation of the engine. The valve assembly may have a valve responsive to the level of fuel in the tank that enables the valve to stay open at a sufficiently low fuel level to permit fuel vapors to flow from the fuel tank into the canister. As the fuel level rises during filling to approach a desired maximum fuel level or quantity of fuel in the tank, a float is raised to close the valve to prevent liquid fuel from flowing through the valve and into the vapor canister. The closed valve also prevents fuel vapor from flowing into the vapor canister. One such system is disclosed in U.S. Pat. No. 5,579,802.
Some of these systems require a high capacity or high flow rate to control the flow of vapor from the fuel tank to the vapor storage canister. Current high capacity or high flow rate valve designs tend to be forced into and held in a closed position, when they should be open, by the vapor pressure in the fuel tank. This prevents vapor from flowing through the valve and into the vapor storage canister defeating the purpose of the system. Further, prior fuel level and vapor vent valves with a single float responsive to the fuel level in the fuel tank to close the valve, maintains the valve closed while the fuel level remains at or near the desired maximum level of fuel in the tank to limit the amount of liquid fuel which undesirably escapes through the valve. Maintaining the valve closed while the fuel level remains at or near the maximum level of fuel in the tank is undesirable because the addition of fuel to the tank when the valve is closed will rapidly increase the pressure within the tank and increase the discharge of hydrocarbon fuel vapors into the atmosphere during filling and in vehicle use prohibit the flow of fuel vapor to the canister.
Further, when a vehicle stops, turns rapidly or is travelling across rough terrain significant splashing or sloshing of fuel in the fuel tank can occur. It has been found that the splashing and sloshing of fuel in the tank is particularly bad when the tank is between xc2xc and xc2xe full. Conventional vapor vent valves permit an undesirable amount of liquid fuel to escape from the fuel tank through the vent valve whereupon it flows to the fuel vapor canister which has a limited volume and storage capacity and is rapidly filled by liquid fuel. Typically, the liquid fuel escapes from conventional vent valves because the outlet thereof is not adequately protected from sloshing or splashing fuel and the valve closure mechanism is not responsive enough to rapidly close the valve and prevent such liquid fuel escape.
Typically, a separate rollover valve is used in a fuel system in series with a vapor vent valve. In normal at rest and operating upright positions or attitudes of the vehicle, the rollover valve is open to permit fuel vapor to flow to the canister and while the vehicle is on its side or rolled over such as in and after an accident, the rollover valve is closed to prevent liquid fuel flow from the tank through the vent valve.
Typical vapor vent valves and rollover valves are mounted within openings through the vehicle fuel tank, and a fuel pump is mounted through a separate opening in the fuel tank. Additional openings through the fuel tank may be provided to mount additional components such as an overpressure relief valve and the like. Each opening through the fuel tank provides a leak path through which hazardous hydrocarbon fuel vapors may escape to the atmosphere.
A high flow rate fuel vapor vent and rollover valve assembly utilizing a float valve that provides a progressive partial closing of a vapor outlet to control the venting of fuel vapors from a fuel tank and the addition of liquid fuel to the tank. A float closes a portion of the vapor outlet in response to liquid fuel at a first level relative to the valve. A body or weight closes the remainder of the vapor outlet in response to rollover of the vehicle to prohibit the escape of liquid fuel and vapor from the vehicle tank during rollover attitudes of the vehicle. One or more separate baffles are constructed and arranged to prevent the escape of liquid fuel through the vapor outlet when the valve is open.
Preferably, to reduce the number of openings in the fuel tank and to simplify manufacture and assembly of the vapor vent and rollover valve assembly, it can be formed at least in part as an integral portion of a fuel pump module disposed within the fuel tank. Ideally, an upper portion of the valve assembly defining the vapor outlet can be formed as an integral portion of a flange of the fuel pump module sealed to the fuel tank. This eliminates a leak path around a separate body of the valve assembly defining the vapor outlet to reduce the likelihood of liquid fuel escaping from the fuel tank. Still further, providing the vapor vent and rollover valve assembly integral with the fuel pump module prevents damage to the valve assembly should a lower portion of the fuel pump module, containing the fuel pump, break away from the upper flange sealed to the fuel tank during a vehicle accident.
Objects, features, and advantages of this invention include providing a vapor vent and rollover valve assembly which has a high flow rate or capacity, opens and closes in response to the level of fuel in the tank, prevents liquid fuel from escaping from the fuel tank to the vapor receiving canister, closes in a vehicle roll-over condition, limits the maximum level of fuel within the fuel tank during filling, enables multiple shut-offs of a fuel filler nozzle during filling of the fuel tank, at least substantially prevents sloshing or splashing liquid fuel from escaping through the vapor outlet, and is rugged, durable, reliable, of relatively simple design and economical manufacture and assembly and has a long useful life in service.